Like terms are
terms that contain the same variables raised to the same power. Only the numerical
coefficients are different. In an expression, only like terms can be combined.
We combine like terms to shorten and simplify algebraic expressions, so we
can work with them more easily. To combine like terms, we add the coefficients
and keep the variables the same. We can't combine unlike terms because that's
like trying to add apples and oranges!

Look at these
10 terms. Let's find all the like terms that can be combined.

all these terms have x2y

all these terms have xy2

this is the only x2yz
term

this is the only xy term

all these terms have x2y2

this is the only xy2z
term

Be careful when combining!
Terms like x2yz and xy2z look a lot alike,
but they aren't and cannot be combined. Write the terms carefully when working
out problems.

Don't overlook terms that are alike!Terms obey the associative property of multiplication - that is, xy and
yx are like terms, as are xy2 andy2x.